Low-pressure absorption refrigerating system including a liquid pump arrangement



Nov. 4, 1-947.

Ilia

LOW PRESSURE ABSORPTION REFRIGERATING SYSTEM P. EDBERG INCLUDING ALIQUID PUMP ARRANGEMENT v Filed Oct. 25, 1944 2 Sheets-Sheet 2 I I; I

INVENTOR ash/ XuATTORNEY be expressly understood,

Patented Nov. 4, 1947 ATIN G SYSTELI INCLUDING ABBAN GEMENT Evansville,Ind, assignor to Send,-

n corporation of Dela- PUMP Per Edberg,

Inc., New York, N. ware a mom Application October 25, 1944, Serial No.560,210

1 The present invention relates to refrigeration and more particularly.to

or the like and the absorbent occurs in' the system as a dilute orconcentrated water solution of the salt. Such systems may include anauxiliary loop circuit for circulating liquid refrigerant to refrigerateor cool at a place remote from the evaporator and/or' an auxiliary loopcircuit for continuously circulating absorption solution in the absorberto promote absorption of refrigerant vapor. Because of the low pressuresat which such systems operate, the usual types of pumps will notfunction satisfactorily in the loop circuits.

One of the objects of the present'invention is to provide a. pump ofnovel construction and so arranged in the loop Another object is toprovide a'pump so arranged in the auxiliary loop circuit as to produceimpeller of the pump.

Another object is to provide a self-contained pump unit of the typeindicated connected to a reservoir to receive liquid by gravity andhaving an hermetically sealed casing extending above and below the levelof the liquid in the reservoir.

Still another object of the present invention is to provide a, pump ofthe type indicated having an impeller housing at its lower end, a motorhousing. at its upper end and an intermediate shaft housing constitutinga penstook for delivering liquid to a combined axial and'radial flowimpeller.

These and other objects will'beoome more apparent from the followingdescription and drawings in which like reference characters denote likeparts throughout the several views. It is to however, that the drawingsare for the purpose of illustration only and not a definition of thelimits of the invention, reference being had for this purpose to .theappended claims.

circuit as to adapt it to cir- I culate liquids in a state close totheir boiling point.

the circulation of liquid in an absorption refrigeration system.

4 Claims. (01. 62-419) 7 In the drawings- Fig. 1 is a diagrammatic viewof an absorption refrigeration system incorporating the novel featuresof thepresent invention and showing the auxiliary loop circuits forcirculating refrigerant and absorption solution; and

Fig. 2 is an enlarged longitudinal sectional view taken on line 2-2 ofFig. 1 showin the construction of the pump in the loop circuit forcirculating refrigerant and the arrangement of the pump with respect tothe evaporator.

In the absorption refrigeration system illustrated in Fig. l of thedrawings, the liquid refrigerant such as, for example, water isintroduced into the evaporator .80 from. a condenser II through a pathof flow including a U-shaped tube -a,hydrostatic head of the liquiddelivered to the generator l6 in'a path of with an outlet vent 21 i2.The evaporator I0 is in the form of a horizontally arranged cylindricaldrum and the 'U-, shaped tube I! has one end connected to a sump l3 atthe bottom of the condenser H with its opposite end extending upwardlythrough the bottom of theevaporator. The refrigerant vapor formed in theevaporator an absorber ll in which into a liquid absorbent such as, forexample, a concentrated water solution of lithium chloride or lithiumbromide. The absorber It also is in the form of horizontally arrangedcylindrical drum and is positioned directly below the evaporator N. Apipe it extends upwardly from the top of the absorber I4 through theevaporator l0, and for a considerable distance above the bottom, toprovide a, standpipe in the evaporaton The standplpe I5 is adapted toexhaust refrigerant vapor from the evaporator In to the absorber I whilemaintaining a body of liquid refrigerant in-the evaporator.

Absorption liquid enriched with refrigerant or. in other words, thedilute salt solution is conducted from the absorber It flow includingthe pump l8, later to be described in detail, conduits l9 and 20, liquidheat exchanger 2| and conduit 22. A plurality of riser tubes 23 areenclosed ina chamber formed by an outer shell '24 of the generator 16and to which steam is supplied through a conduit 25 from a suitablesource of supply. The rate of flow of steam through the conduit 25 iscontrolled by a modulating'valve 2i. Preferably, the steam chamber inthe generator I8 is provided adjacent its upper end and a condensatereturn line 28 adjacent the base thereof. The heating of the riser tubes23 by the v to be expelled from the abwrption solution and such expelledthe vapor is absorbed bottom of the to the base of a vapor is effectiveto raise the absorption solution in the tubes by gas or vapor liftaction. The expelled vapor passes from the upper ends of the riser tubes23 into a vapor separator 29 and thence flows through a. conduit 30 tothe condenser H, where the vapor is liquefied. Liquid refrigerant formedin the condenser flows through the U-shaped tube I2 to the evaporatorI0, as explained above, to complete the refrigeration cycle.

The raised absorption solution from which refrigerant vapor has beenexpelled is conducted from the upper part of the generator l6 to theabsorber l4 in a path of flow including a conduit 3|, chamber 32,conduit 33, liquid heat exchanger 2| and conduit 34. The upper end ofthe conduit 34 extends into the upper portion of the absorber |4adjacent the inlet from the standpipe l5 and has a plurality ofapertures or nozzles therein to provide a distributing pipe 35 fordividing the absorption solution as it is introduced into the absorberto promote absorption of the refrigerant vapor. The heat liberated bythe absorption of refrigerant vapor in absorber I4 is taken up by acooling medium such as, for example, water which flows upwardly througha bank of vertically disposed pipes or coils 36 in the absorber. Thecooling water is introduced into the lower ends of the bank of pipes 36from a supply main 3'! and is discharged from the upper ends of the bankof pipes through a conduit 38. Conduit 38 is connected to the condenserso that the cooling water also may be utilized to effect cooling of thecondenser. The cooling water is discharged from the condenser I througha conduit 39.

The system operates in a partial vacuum with the generator l6 andcondenser operating at one pressure and the evaporator I0 and absorber|4 operating at a lower pressure. The pressure differential between thehigh and low'pressure sides of the system is maintained by a liquidcolumn in the up-leg of the U-shaped tube |2 between the condenser IIand evaporator ID. A similar liquid column also is present in theconduit 34 connecting the absorber l4 and liquid heat exchanger 2|. Thepressure differential between the absorber I4 and generator l6 also ismaintained by the pump |8 connected between the absorber and conduit 20.

To prevent the progressive concentration of the absorption solutionunder certain conditions of operation and the crystallization andprecipitation of salt resulting from such progressive concentration acontrol means is provided which is responsive to the concentration ofthe absorption solution and connected to adjust the valve 26 to regulatethe amount of steam supplied to through a flexible bellows 42 to permitrelative movement and the arm is pivoted at 43. The outer end of the arm4| constitutes the movable contact 44 of a rheostat 45 connected bymeans of the electric circuit 46 to a servo-motor 41 & for operating thesteam control valve 26. The

the generator [6. The control means may be I located in any part of therefrigeration system where the progressive concentration of theabsorption solution is likely to occur. As illustrated in Fig. 1 of thedrawings, the control means is located in the chamber 32 in the returnline between the generator l6 and heat exchanger 2|. The controlcomprises a float 40 having a specific gravity such as to adapt it torise when the concentration of the absorption solution approaches asaturation point where salt will precipitate out of the solution. Whenthe absorption solution is diluted suificiently to prevent precipitationof salt, the float 40 will fall by gravity in the absorption solution tothe position illustrated in Fig. 1.

The concentration control float 40 has an arm 4| extending outwardlyfrom the chamber 32 flexible bellows 42 acts as a. load spring to causethe contact arm 44 to vary the resistance directly in response tovariations in the concentration of the-solution to modulate the valve26. Preferably, a baflle plate 48 is provided in the chamber 32 adjacentthe end'of the conduit 3| to prevent the velocity of the stream ofincoming absorption solution from affecting the operation of the controlfloat 40. The end of the conduit 33 extends upwardly in the chamber 32above the float to insure immersion of the control float 40 by theabsorption solution.

Preferably, an overflow by-pass 50 is provided between the separatingchamber 29 of the generator I6 and the bottom of the absorber l4. As

illustrated in Fig. 1 of the drawings, the upper In accordance with thepresent invention, the liquid refrigerant in the evaporator I0 iscirculated continuously in a loop circuit to adapt the system torefrigerate at a place remote from the evaporator. The loop circuitcomprises a pump 55, conduit 56, cooling element 51 and conduit 58. Thepump 55 is connected to receive liquid refrigerant from the evaporatorH) in a manner later to be described in detail and delivers the liquidrefrigerant to the conduit 56. The conduit 56 is connected between theoutlet from the pump 55 and the inlet to the cooling element 5'! and theconduit 58 is connected between the outlet from the cooling element andthe upper part ofthe evaporator Hi. The cooling element 51 isillustrated diagrammatically as a cooling coil but it will be understoodthat this element may have other forms such as a radiator or the likedepending upon the particular installation. As illustrated in Fig. 1 ofthe drawings, the outlet end of the conduit 58 extends into theevaporator l0 and is provided with a series of apertures or nozzles toprovide a spray pipe 59 for dividing the liquid refrigerant into a sprayas it is returned to the evaporator to promote evaporation.

Preferably a baffle plate 60 is provided in the evaporator I0 betweentheend of the spray pipe 59 and the standpipe |5 to prevent the liquidrefrigerant from being swept into the standpipe with the refrigerantvapor.

As illustrated in Fig. 2, the pump 55 comprises a lower pump housing 64,an upper motor housing 65 and an intermediate shaft housing 66. Thehousings 64, 65 and 66 are connected and sealed to each other as bywelding or the like to provide a continuous hermetically sealed casing.The pump casing is positioned adjacent the evaporator I0 and extendsabove and below the level L of the liquid in the evaporator l0. Aninclined conduit 61 is connected between the side of the evaporator I0below the liquid level and the side of the shaft housing 66 so thatrefrigerant liquid will flow by gravity into the casing and' rise to thelevel L therein. Preferably, a strainer 68 is provided in the conduit 61to filter out any foreign matter which may occur in the system. A venttube 69 is connected between the evaporator l0 and the shaft. housingportion 66 ofpthe pump casingabove the liquid level L to balance thepressure in the casing and evaporator.

A combined axial and radial flow centrifugal impeller 10 is mounted inthe pump housing 64 for rotation therein. The impeller I has arelatively large axial intake opening 'II which leads into a pluralityof radial channels I2. The pump housing 64- has an annular pressurechamber 14 surrounding the periphery of the impeller I0 with an outletport I5. The pump-housing 64 also has a radial flange 16 surrounding theport I which is connected to the cooperating flange 'I'I ofa conduit. 56and preferably the flanges are welded .to each other to hermeticallyseal the joint.

Whilethe impeller I0 may be rotated by any suitable prime mover such asan hydraulic motor,

an electric motor 80, preferably, is provided forthis purpose. Theelectric motor 80 comprises a stator having the usual field coils 8| anda rotor 82. The motor housing 65 is made in two parts to adapt the motor80 to be assembled therein and kept at a minimum for the most efficientoperation.

The absorption solution in the absorber I4 also is circulatedcontinuously through an auxiliary loop circuit to promote absorption ofthe refri erant 'vapor. The auxiliary loop circuit for the absorptionsolution comprises the pump I8 and the cover 83 of the housing may beattached v thereto by means of bolts 84 or by welding the cooperatingflanges. If the bolts 84 are used, the

motor housing 65 must be hermetically sealed by means of, a suitablepacking not herein shown. The cover 83 of the motor housing 65 is formedwith a plurality of fins 85 for dissipating',the heat generated in thehousing. Conduits 86 for supplying current to the electric motor 80extend through a bushing 81 in the cover 83 which is so constructed asto hermetically seal the joint. Because of the relatively low pressureswhich occur in the motor housing 65, 5 to 10 mm.- Hg absolute, thedischarge voltage between uninsulate'd conductors is only aboutone-fifth of that occurring at atmospheric pressure. Th electricalconductors in the motor 80, therefore, are heavily insulated to preventelectric leakage in the housing.

The rotor 82 of the motor 80 is connected to the impeller 10 by a shaft90. The upper end of the shaft 96 extends through an axial bore ill inthe rotor 82 and is keyed thereto for rotation as a unit. Rotor 82 restson a step or annular shoulder 92 on the shaft 90 and is held in seatingengagement with the shoulder by a nut 93. The shaft 90 and rotor 82 aresupported for rotation by an anti-friction thrust bearing 94 mounted inan annular sleeve 95 forming part of the housing 65. Above the bearing94 is a packing 96 surrounding the shaft and held in place by a glandnut 91. The annular sleeve 95 and packing 96 provide a 1 well formaintaining a supply of lubricant which is fed to the bearing by an oilslinger 98. The

' joint between the body portion and cover of the well for lubricantformed by the annular sleeve rator means of a nut I03. The liquid in theshaft housing as acts to steady the shaft 90 as it rotates therein butthe shaft is further supported ad-.

jacent its lower end by a bearing I04 supported by a sleeve I05 in theshaft housing 66. The bearing I04 is lubricated by the liquidrefrigerant flowing through the shaft housing 66 to the imconduit I9.The pump I8 is of a construction identical with the pump 55 and isarranged at the side of the absorber I4 with a conduit IIO connectingthe absorber and shaft housing 66 of the pump. The conduit I9 isconnected at one end to the outlet from the pump I8 and its opposite endIII extends horizontally into the absorber I4 throughout substantiallythe entire lengthof the latter. The horizontally extending portion IIIof the conduit I9 is provided with a plurality of spray headsI I2, eachof which comprises a nozzle and a deflecting plate for dividing theabsorption solution into a spray and distributing the spray over thebank of cooling coils 36 to promote absorption of the refrigerant,During operation of the refrigeration system, part of the circulatingsolution is diverted from the conduit I9 through the conduit 20 and heatexchanger 2I to the generator I6 as previously described. One form ofthe invention having now been described in detail the modeof operationis explained-as follows.

-For purposes of description let it be assumed that the system is notoperating and the concentration control fioat- 40 is in theposition-illustrated in Fig. 1 of the drawings To initiate operation ofthe refrigeration system steam is supplied through the conduit 25 to thegenerator I6 and Water is supplied from the main 31 to the cooling coils36 in the absorber I4 and through the conduit 38 to the condenser II.Simultaneously, current is supplied to the electric motors of the pumpsI8 and 55 to rotate the impellers I0 to circulate refrigerant andabsorbent solution in their respective auxiliary loop circuits. With thefloat 40 in the position illustrated in. Fig. 1,

the rheostat will be adjusted to supply steam to the generator I 6 forfull load conditions. The steam in the generator I6 will expel watervapor from the absorption solution standing in the riser tubes 23 andthe water vapor will rise in the tubes to the vapor separating chamber.29 and raise the absorption solution by vapor lift action. In thechamber 29, the refrigerant vapor will be separated from the absorptionliquid and will pass through the conduit 30 to the condenser II wherethe vapor will be liquefied by its contact with the relatively coldtubes therein. The liquefied refrigerant in the condenser then will flowby gravity into the sump I3 and through the U-shaped tube I2 to theevaporator I0.

The liquid refrigerant delivered to the evapo- I0 will accumulatetherein around the standpipe I5 and will flow through the conduit 61into the shaft housing 66 of the pump casing. Due to the vent tube 69connecting the evaporator I0 and shaft housing 06 above the liquid levelL the liquid refrigerant is free to rise in the shaft housing to thesame level as in the evaporator. .Thus the shaft housing 66 is in thenature of a penstock for maintaining a hydrostatic head of therefrigerant liquid above the impeller I0. The refrigerant liquid willflow by gravity into the axial opening II in the hub of the impeller land then lnto the radial passages 12. Due to the rotation of theimpeller10 the liquid in the radial passages 12 issubjected to centrifugal forcewhich substantially increases its velocity and delivers it to thepressure: chamber 14 surrounding the impeller. The chamber 14 convertsthe velocity head of the liquid refrigerant discharged from the impeller10 to apressure head and discharges the liquid through the outlet port15 to the conduit 55. It will be noted that the liquid refrigerantsupplied to the impeller 10 is at v all times under pressuer due to thehydrostatic head in the shaft housing so that there is no tendency forthe liquid to vaporize and cause the pump to become suction bound.

The liquid refrigerant leaving the pump 55 will be conducted through theconduit 56, cooling element and conduit 58back to the evaporator l0solution through the auxiliary 100p circuit prothrough separate paths inthe heat exchanger 2 I,

where it will be sprayed through the nozzles in the spray pipe 59.During the passage of the liquid refrigerant through the cooling element51, it will pick up heat from the surrounding ambient such as a streamof air or a'liquid to be cooled. Due to the pressure of the liquidrefrigerant circulating in the auxiliary loop circuit little if anyevaporation will occur but instead the heat will .be received assensible heat to increase the temperature of the refrigerant. When therefrigerant is delivered to the evaporator l0 through the spray pipe 59the low pressure prevailing therein will cause evaporation of a part ofthe refrigerant with a conversion of its sensible heat to latent heat ofvaporization thereby reducing its temperature and the temperature of thebody of refrigerant in the evaporator. Thus the circulating refrigerantoperates to absorb heat from the ambient surrounding the cooling element51 and a portion of the refrigerant evaporates in the evap-' orator toreduce its temperature.

The refrigerant vapor in the evaporator ID will flow through thestandpipe IE to the absorber l4. Simultaneously with the introduction ofthe refrigerant vapor into the absorber It, the concentrated absorptionsolution in the separating chamber 29 will flow through the conduit 3|,chamber 32, conduit 33, heat exchanger- 2|, conduit 34 and spray pipe,35 which delivers it into the top of the absorber adjacent thestandpipe l5 as a spray. Thus there will be an intimate mixture of therefrigerant vapor with the finely divided concentrated absorptionsolution, Due to the afiinity of the concentrated absorption solutionfor the refrigerant vapor, the latter will be absorbed in the solution.

Absorption solution also will be circulated in the auxiliary loopcircuit comprising the pump I8 and conduit l9 which will deliver thesolution back to the absorber through the spray heads H2 on the spraypipe Ill. The absorption solution is delivered to the pump H3 in amanner identical with that described with respect to the flow ofrefrigerant into the pump 55. The shaft housing of the pump 18 acts as apenstock to maintain a hydrostatic head of the absorption solutiondelivered to the impeller of the pump so that the solution is maintainedunder pressure as it flows through the pump.

The heat of absorption is transferred to the cooling water circulatingthrough the cooling coils 36 in the absorber M. The rapid absorption ofthe refrigerant vapor in the absorber M will tend to reduce the pressuretherein causing the refrigerant vapor in the evaporator I!) to be drawnthrough the standpipe 15. It will be observed, therefore, that thecirculation of the absorption the dilute solution fiowingto thegenerator is heated by the concentrated solution flowing to the absorberwhich gives up its heat and becomes colder.

During the operation of the refrigeration system any abnormal conditioncausing a, change in the concentration of the absorption solutionflowing through the chamber 32 will actuate the float 40 to adjust therheostat 45 and thereby adjust the servo-motor 41 and valve 26 forcontrollin the flow of steam to the generator 16. If the concentrationof the absorption solution increases the float 40 rises which, in turn,partially closes the valve 26 to decrease the flow of steam to thegenerator l6. Upon a decrease in the concentration of the absorptionsolution, the float 40 will fall by gravity which operating through therheostat 45 and servo-motor 41 will open the valve 26 to supply moresteam to the generator Hi.

It will now be observed from the foregoing specification that thepresent invention provides a novel construction and arrangement of pumpfor use in the auxiliary loop circuits of an absorption refrigerationsystem for circulating refrigerant and absorption solution. It also willbe observed that the present invention provides a.

to receive liquid from an element of the refrigeration system bygravity.

While a, preferred form of the invention is 4 herein illustrated anddescribed it will be understood by those skilled in the art that variouschanges may be made in the construction and arrangement of the partswithout departing from the spirit or scope of the invention. Reference,therefore, is to be had to the claims appended hereto for a definitionof the scope of the invention.

What is claimed is:

1. In an absorption refrigeration system having a plurality ofinterconnected elements, a pump housing below the liquid level in one ofthe elements and having an impeller therein, a motor housing above theliquid level in said element and having an electric motor therein, ashaft housing extending between the pump and motor housings, saidhousings being connected to provide an hermetically sealed casing, ashaft in the shaft housing connecting the electric motor and impeller, aconduit connecting the element and shaft housing intermediate the endsof the latter for supplying liquid from the element to the casing bygravity, a vent between the shaft and motor housings, and a check valvein the vent to permit equalizing of the pressure therebetween whilepreventing the' splashing of liquid into the motor housing.

2. In an absorption refrigeration system of the type which operates in apartial vacuum, a genthe evaporator and easing intermediate the ends ofthe latter for supplying liquid from the element to the casing bygravity, a housing formed by the casing for enclosing the prime mover;and a check valve in the housing for equalizing pressure whilepreventing the splashing of liquid into the motor housing.

3. In an absorption refrigeration system of the type which operates in apartial vacuum, a generator, a condenser, an evaporator, an absorber,means interconnecting the elements to provide circuits for refrigerantand absorbent, an auxiliary loop circuit connected to circulateabsorption solution in the absorber, and a pump in said auxiliary loopcircuit having an hermetically sealed casing extending above and belowthe level of the absorption solution in the absorber, a shaft extendingthroughout the length of the casing, an impeller at the lower end of theshaft, a prime mover at the upper end of the shaft, a conduit the primemover, and a check valve in the hou sing for equalizing pressure whilepreventing the splashing of liquid into the motor housing.

4. In an absorption refrigeration system of the type which operates in apartial vacuum, a generator, a condenser, an evaporator, an absorber,

Number connecting the element and casing intermediate the ends of thelatter for supplying absorption solution from the element to the casingby gravity, a housing formed by the casing for enclosing meansinterconnecting the elements to provide circuits for refrigerant andabsorbent, an auxiliary loop circuit connected to circulate refrigerantin the evaporator, an auxiliary loop circuit connected to circulateabsorption solution in the absorber, each of the auxiliary loop circuitshaving a pump comprising a pump housing below the liquid level with animpeller therein, a motor housing above the liquid level with anelectric motor therein, a shaft housing extending between the pump andmotor housings, said housings being connected to provide an hermeticallysealed casing, a shaft in the shaft housing connecting the electricmotor and impeller, a conduit connected to the shaft housing forsupplying liquid by gravity to the pump housing and applying ahydrostatic head on the impeller, a vent between the shaft and motorhousings, and a check valve in the vent to permit equalizing of thepressure therebetween while preventing the splashingoi' liquid into themotor housing.

' PER EDBERG. I

file of this 1 patent:

UNITED STATES PATENTS Name Date 2,019,290 Brace Oct. 29, 1935 2,225,491Voorhees et a1 Dec. 1'7, 1940 2,298,924 Bichowsky Oct. 13, 1942

